diff --git a/changelog.d/12208.misc b/changelog.d/12208.misc
new file mode 100644
index 000000000..c5b635679
--- /dev/null
+++ b/changelog.d/12208.misc
@@ -0,0 +1 @@
+Add type hints to tests files.
\ No newline at end of file
diff --git a/mypy.ini b/mypy.ini
index c8390ddba..f9c39fcaa 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -90,7 +90,6 @@ exclude = (?x)
    |tests/push/test_push_rule_evaluator.py
    |tests/rest/client/test_transactions.py
    |tests/rest/media/v1/test_media_storage.py
-   |tests/rest/media/v1/test_url_preview.py
    |tests/scripts/test_new_matrix_user.py
    |tests/server.py
    |tests/server_notices/test_resource_limits_server_notices.py
diff --git a/tests/rest/client/test_transactions.py b/tests/rest/client/test_transactions.py
index 3b5747cb1..8d8251b2a 100644
--- a/tests/rest/client/test_transactions.py
+++ b/tests/rest/client/test_transactions.py
@@ -1,3 +1,18 @@
+# Copyright 2018-2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from http import HTTPStatus
 from unittest.mock import Mock, call
 
 from twisted.internet import defer, reactor
@@ -11,14 +26,14 @@ from tests.utils import MockClock
 
 
 class HttpTransactionCacheTestCase(unittest.TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
         self.clock = MockClock()
         self.hs = Mock()
         self.hs.get_clock = Mock(return_value=self.clock)
         self.hs.get_auth = Mock()
         self.cache = HttpTransactionCache(self.hs)
 
-        self.mock_http_response = (200, "GOOD JOB!")
+        self.mock_http_response = (HTTPStatus.OK, "GOOD JOB!")
         self.mock_key = "foo"
 
     @defer.inlineCallbacks
diff --git a/tests/rest/media/v1/test_media_storage.py b/tests/rest/media/v1/test_media_storage.py
index cba9be17c..7204b2dfe 100644
--- a/tests/rest/media/v1/test_media_storage.py
+++ b/tests/rest/media/v1/test_media_storage.py
@@ -16,7 +16,7 @@ import shutil
 import tempfile
 from binascii import unhexlify
 from io import BytesIO
-from typing import Optional
+from typing import Any, BinaryIO, Dict, List, Optional, Union
 from unittest.mock import Mock
 from urllib import parse
 
@@ -26,18 +26,24 @@ from PIL import Image as Image
 
 from twisted.internet import defer
 from twisted.internet.defer import Deferred
+from twisted.test.proto_helpers import MemoryReactor
 
+from synapse.events import EventBase
 from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.logging.context import make_deferred_yieldable
+from synapse.module_api import ModuleApi
 from synapse.rest import admin
 from synapse.rest.client import login
 from synapse.rest.media.v1._base import FileInfo
 from synapse.rest.media.v1.filepath import MediaFilePaths
-from synapse.rest.media.v1.media_storage import MediaStorage
+from synapse.rest.media.v1.media_storage import MediaStorage, ReadableFileWrapper
 from synapse.rest.media.v1.storage_provider import FileStorageProviderBackend
+from synapse.server import HomeServer
+from synapse.types import RoomAlias
+from synapse.util import Clock
 
 from tests import unittest
-from tests.server import FakeSite, make_request
+from tests.server import FakeChannel, FakeSite, make_request
 from tests.test_utils import SMALL_PNG
 from tests.utils import default_config
 
@@ -46,7 +52,7 @@ class MediaStorageTests(unittest.HomeserverTestCase):
 
     needs_threadpool = True
 
-    def prepare(self, reactor, clock, hs):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.test_dir = tempfile.mkdtemp(prefix="synapse-tests-")
         self.addCleanup(shutil.rmtree, self.test_dir)
 
@@ -62,7 +68,7 @@ class MediaStorageTests(unittest.HomeserverTestCase):
             hs, self.primary_base_path, self.filepaths, storage_providers
         )
 
-    def test_ensure_media_is_in_local_cache(self):
+    def test_ensure_media_is_in_local_cache(self) -> None:
         media_id = "some_media_id"
         test_body = "Test\n"
 
@@ -105,7 +111,7 @@ class MediaStorageTests(unittest.HomeserverTestCase):
         self.assertEqual(test_body, body)
 
 
-@attr.s(slots=True, frozen=True)
+@attr.s(auto_attribs=True, slots=True, frozen=True)
 class _TestImage:
     """An image for testing thumbnailing with the expected results
 
@@ -121,18 +127,18 @@ class _TestImage:
             a 404 is expected.
     """
 
-    data = attr.ib(type=bytes)
-    content_type = attr.ib(type=bytes)
-    extension = attr.ib(type=bytes)
-    expected_cropped = attr.ib(type=Optional[bytes], default=None)
-    expected_scaled = attr.ib(type=Optional[bytes], default=None)
-    expected_found = attr.ib(default=True, type=bool)
+    data: bytes
+    content_type: bytes
+    extension: bytes
+    expected_cropped: Optional[bytes] = None
+    expected_scaled: Optional[bytes] = None
+    expected_found: bool = True
 
 
 @parameterized_class(
     ("test_image",),
     [
-        # smoll png
+        # small png
         (
             _TestImage(
                 SMALL_PNG,
@@ -193,11 +199,17 @@ class MediaRepoTests(unittest.HomeserverTestCase):
     hijack_auth = True
     user_id = "@test:user"
 
-    def make_homeserver(self, reactor, clock):
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
 
         self.fetches = []
 
-        def get_file(destination, path, output_stream, args=None, max_size=None):
+        def get_file(
+            destination: str,
+            path: str,
+            output_stream: BinaryIO,
+            args: Optional[Dict[str, Union[str, List[str]]]] = None,
+            max_size: Optional[int] = None,
+        ) -> Deferred:
             """
             Returns tuple[int,dict,str,int] of file length, response headers,
             absolute URI, and response code.
@@ -238,7 +250,7 @@ class MediaRepoTests(unittest.HomeserverTestCase):
 
         return hs
 
-    def prepare(self, reactor, clock, hs):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
 
         media_resource = hs.get_media_repository_resource()
         self.download_resource = media_resource.children[b"download"]
@@ -248,8 +260,9 @@ class MediaRepoTests(unittest.HomeserverTestCase):
 
         self.media_id = "example.com/12345"
 
-    def _req(self, content_disposition, include_content_type=True):
-
+    def _req(
+        self, content_disposition: Optional[bytes], include_content_type: bool = True
+    ) -> FakeChannel:
         channel = make_request(
             self.reactor,
             FakeSite(self.download_resource, self.reactor),
@@ -288,7 +301,7 @@ class MediaRepoTests(unittest.HomeserverTestCase):
 
         return channel
 
-    def test_handle_missing_content_type(self):
+    def test_handle_missing_content_type(self) -> None:
         channel = self._req(
             b"inline; filename=out" + self.test_image.extension,
             include_content_type=False,
@@ -299,7 +312,7 @@ class MediaRepoTests(unittest.HomeserverTestCase):
             headers.getRawHeaders(b"Content-Type"), [b"application/octet-stream"]
         )
 
-    def test_disposition_filename_ascii(self):
+    def test_disposition_filename_ascii(self) -> None:
         """
         If the filename is filename=<ascii> then Synapse will decode it as an
         ASCII string, and use filename= in the response.
@@ -315,7 +328,7 @@ class MediaRepoTests(unittest.HomeserverTestCase):
             [b"inline; filename=out" + self.test_image.extension],
         )
 
-    def test_disposition_filenamestar_utf8escaped(self):
+    def test_disposition_filenamestar_utf8escaped(self) -> None:
         """
         If the filename is filename=*utf8''<utf8 escaped> then Synapse will
         correctly decode it as the UTF-8 string, and use filename* in the
@@ -335,7 +348,7 @@ class MediaRepoTests(unittest.HomeserverTestCase):
             [b"inline; filename*=utf-8''" + filename + self.test_image.extension],
         )
 
-    def test_disposition_none(self):
+    def test_disposition_none(self) -> None:
         """
         If there is no filename, one isn't passed on in the Content-Disposition
         of the request.
@@ -348,26 +361,26 @@ class MediaRepoTests(unittest.HomeserverTestCase):
         )
         self.assertEqual(headers.getRawHeaders(b"Content-Disposition"), None)
 
-    def test_thumbnail_crop(self):
+    def test_thumbnail_crop(self) -> None:
         """Test that a cropped remote thumbnail is available."""
         self._test_thumbnail(
             "crop", self.test_image.expected_cropped, self.test_image.expected_found
         )
 
-    def test_thumbnail_scale(self):
+    def test_thumbnail_scale(self) -> None:
         """Test that a scaled remote thumbnail is available."""
         self._test_thumbnail(
             "scale", self.test_image.expected_scaled, self.test_image.expected_found
         )
 
-    def test_invalid_type(self):
+    def test_invalid_type(self) -> None:
         """An invalid thumbnail type is never available."""
         self._test_thumbnail("invalid", None, False)
 
     @unittest.override_config(
         {"thumbnail_sizes": [{"width": 32, "height": 32, "method": "scale"}]}
     )
-    def test_no_thumbnail_crop(self):
+    def test_no_thumbnail_crop(self) -> None:
         """
         Override the config to generate only scaled thumbnails, but request a cropped one.
         """
@@ -376,13 +389,13 @@ class MediaRepoTests(unittest.HomeserverTestCase):
     @unittest.override_config(
         {"thumbnail_sizes": [{"width": 32, "height": 32, "method": "crop"}]}
     )
-    def test_no_thumbnail_scale(self):
+    def test_no_thumbnail_scale(self) -> None:
         """
         Override the config to generate only cropped thumbnails, but request a scaled one.
         """
         self._test_thumbnail("scale", None, False)
 
-    def test_thumbnail_repeated_thumbnail(self):
+    def test_thumbnail_repeated_thumbnail(self) -> None:
         """Test that fetching the same thumbnail works, and deleting the on disk
         thumbnail regenerates it.
         """
@@ -443,7 +456,9 @@ class MediaRepoTests(unittest.HomeserverTestCase):
                 channel.result["body"],
             )
 
-    def _test_thumbnail(self, method, expected_body, expected_found):
+    def _test_thumbnail(
+        self, method: str, expected_body: Optional[bytes], expected_found: bool
+    ) -> None:
         params = "?width=32&height=32&method=" + method
         channel = make_request(
             self.reactor,
@@ -485,7 +500,7 @@ class MediaRepoTests(unittest.HomeserverTestCase):
             )
 
     @parameterized.expand([("crop", 16), ("crop", 64), ("scale", 16), ("scale", 64)])
-    def test_same_quality(self, method, desired_size):
+    def test_same_quality(self, method: str, desired_size: int) -> None:
         """Test that choosing between thumbnails with the same quality rating succeeds.
 
         We are not particular about which thumbnail is chosen."""
@@ -521,7 +536,7 @@ class MediaRepoTests(unittest.HomeserverTestCase):
             )
         )
 
-    def test_x_robots_tag_header(self):
+    def test_x_robots_tag_header(self) -> None:
         """
         Tests that the `X-Robots-Tag` header is present, which informs web crawlers
         to not index, archive, or follow links in media.
@@ -540,29 +555,38 @@ class TestSpamChecker:
     `evil`.
     """
 
-    def __init__(self, config, api):
+    def __init__(self, config: Dict[str, Any], api: ModuleApi) -> None:
         self.config = config
         self.api = api
 
-    def parse_config(config):
+    def parse_config(config: Dict[str, Any]) -> Dict[str, Any]:
         return config
 
-    async def check_event_for_spam(self, foo):
+    async def check_event_for_spam(self, event: EventBase) -> Union[bool, str]:
         return False  # allow all events
 
-    async def user_may_invite(self, inviter_userid, invitee_userid, room_id):
+    async def user_may_invite(
+        self,
+        inviter_userid: str,
+        invitee_userid: str,
+        room_id: str,
+    ) -> bool:
         return True  # allow all invites
 
-    async def user_may_create_room(self, userid):
+    async def user_may_create_room(self, userid: str) -> bool:
         return True  # allow all room creations
 
-    async def user_may_create_room_alias(self, userid, room_alias):
+    async def user_may_create_room_alias(
+        self, userid: str, room_alias: RoomAlias
+    ) -> bool:
         return True  # allow all room aliases
 
-    async def user_may_publish_room(self, userid, room_id):
+    async def user_may_publish_room(self, userid: str, room_id: str) -> bool:
         return True  # allow publishing of all rooms
 
-    async def check_media_file_for_spam(self, file_wrapper, file_info) -> bool:
+    async def check_media_file_for_spam(
+        self, file_wrapper: ReadableFileWrapper, file_info: FileInfo
+    ) -> bool:
         buf = BytesIO()
         await file_wrapper.write_chunks_to(buf.write)
 
@@ -575,7 +599,7 @@ class SpamCheckerTestCase(unittest.HomeserverTestCase):
         admin.register_servlets,
     ]
 
-    def prepare(self, reactor, clock, hs):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.user = self.register_user("user", "pass")
         self.tok = self.login("user", "pass")
 
@@ -586,7 +610,7 @@ class SpamCheckerTestCase(unittest.HomeserverTestCase):
 
         load_legacy_spam_checkers(hs)
 
-    def default_config(self):
+    def default_config(self) -> Dict[str, Any]:
         config = default_config("test")
 
         config.update(
@@ -602,13 +626,13 @@ class SpamCheckerTestCase(unittest.HomeserverTestCase):
 
         return config
 
-    def test_upload_innocent(self):
+    def test_upload_innocent(self) -> None:
         """Attempt to upload some innocent data that should be allowed."""
         self.helper.upload_media(
             self.upload_resource, SMALL_PNG, tok=self.tok, expect_code=200
         )
 
-    def test_upload_ban(self):
+    def test_upload_ban(self) -> None:
         """Attempt to upload some data that includes bytes "evil", which should
         get rejected by the spam checker.
         """
diff --git a/tests/rest/media/v1/test_url_preview.py b/tests/rest/media/v1/test_url_preview.py
index da2c53326..5148c3987 100644
--- a/tests/rest/media/v1/test_url_preview.py
+++ b/tests/rest/media/v1/test_url_preview.py
@@ -16,16 +16,21 @@ import base64
 import json
 import os
 import re
+from typing import Any, Dict, Optional, Sequence, Tuple, Type
 from urllib.parse import urlencode
 
 from twisted.internet._resolver import HostResolution
 from twisted.internet.address import IPv4Address, IPv6Address
 from twisted.internet.error import DNSLookupError
-from twisted.test.proto_helpers import AccumulatingProtocol
+from twisted.internet.interfaces import IAddress, IResolutionReceiver
+from twisted.test.proto_helpers import AccumulatingProtocol, MemoryReactor
 
 from synapse.config.oembed import OEmbedEndpointConfig
+from synapse.rest.media.v1.media_repository import MediaRepositoryResource
 from synapse.rest.media.v1.preview_url_resource import IMAGE_CACHE_EXPIRY_MS
+from synapse.server import HomeServer
 from synapse.types import JsonDict
+from synapse.util import Clock
 from synapse.util.stringutils import parse_and_validate_mxc_uri
 
 from tests import unittest
@@ -52,7 +57,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         b"</head></html>"
     )
 
-    def make_homeserver(self, reactor, clock):
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
 
         config = self.default_config()
         config["url_preview_enabled"] = True
@@ -113,22 +118,22 @@ class URLPreviewTests(unittest.HomeserverTestCase):
 
         return hs
 
-    def prepare(self, reactor, clock, hs):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
 
         self.media_repo = hs.get_media_repository_resource()
         self.preview_url = self.media_repo.children[b"preview_url"]
 
-        self.lookups = {}
+        self.lookups: Dict[str, Any] = {}
 
         class Resolver:
             def resolveHostName(
                 _self,
-                resolutionReceiver,
-                hostName,
-                portNumber=0,
-                addressTypes=None,
-                transportSemantics="TCP",
-            ):
+                resolutionReceiver: IResolutionReceiver,
+                hostName: str,
+                portNumber: int = 0,
+                addressTypes: Optional[Sequence[Type[IAddress]]] = None,
+                transportSemantics: str = "TCP",
+            ) -> IResolutionReceiver:
 
                 resolution = HostResolution(hostName)
                 resolutionReceiver.resolutionBegan(resolution)
@@ -140,9 +145,9 @@ class URLPreviewTests(unittest.HomeserverTestCase):
                 resolutionReceiver.resolutionComplete()
                 return resolutionReceiver
 
-        self.reactor.nameResolver = Resolver()
+        self.reactor.nameResolver = Resolver()  # type: ignore[assignment]
 
-    def create_test_resource(self):
+    def create_test_resource(self) -> MediaRepositoryResource:
         return self.hs.get_media_repository_resource()
 
     def _assert_small_png(self, json_body: JsonDict) -> None:
@@ -153,7 +158,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         self.assertEqual(json_body["og:image:type"], "image/png")
         self.assertEqual(json_body["matrix:image:size"], 67)
 
-    def test_cache_returns_correct_type(self):
+    def test_cache_returns_correct_type(self) -> None:
         self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
 
         channel = self.make_request(
@@ -207,7 +212,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             channel.json_body, {"og:title": "~matrix~", "og:description": "hi"}
         )
 
-    def test_non_ascii_preview_httpequiv(self):
+    def test_non_ascii_preview_httpequiv(self) -> None:
         self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
 
         end_content = (
@@ -243,7 +248,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         self.assertEqual(channel.code, 200)
         self.assertEqual(channel.json_body["og:title"], "\u0434\u043a\u0430")
 
-    def test_video_rejected(self):
+    def test_video_rejected(self) -> None:
         self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
 
         end_content = b"anything"
@@ -279,7 +284,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_audio_rejected(self):
+    def test_audio_rejected(self) -> None:
         self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
 
         end_content = b"anything"
@@ -315,7 +320,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_non_ascii_preview_content_type(self):
+    def test_non_ascii_preview_content_type(self) -> None:
         self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
 
         end_content = (
@@ -350,7 +355,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         self.assertEqual(channel.code, 200)
         self.assertEqual(channel.json_body["og:title"], "\u0434\u043a\u0430")
 
-    def test_overlong_title(self):
+    def test_overlong_title(self) -> None:
         self.lookups["matrix.org"] = [(IPv4Address, "10.1.2.3")]
 
         end_content = (
@@ -387,7 +392,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         # We should only see the `og:description` field, as `title` is too long and should be stripped out
         self.assertCountEqual(["og:description"], res.keys())
 
-    def test_ipaddr(self):
+    def test_ipaddr(self) -> None:
         """
         IP addresses can be previewed directly.
         """
@@ -417,7 +422,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             channel.json_body, {"og:title": "~matrix~", "og:description": "hi"}
         )
 
-    def test_blacklisted_ip_specific(self):
+    def test_blacklisted_ip_specific(self) -> None:
         """
         Blacklisted IP addresses, found via DNS, are not spidered.
         """
@@ -438,7 +443,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_blacklisted_ip_range(self):
+    def test_blacklisted_ip_range(self) -> None:
         """
         Blacklisted IP ranges, IPs found over DNS, are not spidered.
         """
@@ -457,7 +462,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_blacklisted_ip_specific_direct(self):
+    def test_blacklisted_ip_specific_direct(self) -> None:
         """
         Blacklisted IP addresses, accessed directly, are not spidered.
         """
@@ -476,7 +481,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         )
         self.assertEqual(channel.code, 403)
 
-    def test_blacklisted_ip_range_direct(self):
+    def test_blacklisted_ip_range_direct(self) -> None:
         """
         Blacklisted IP ranges, accessed directly, are not spidered.
         """
@@ -493,7 +498,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_blacklisted_ip_range_whitelisted_ip(self):
+    def test_blacklisted_ip_range_whitelisted_ip(self) -> None:
         """
         Blacklisted but then subsequently whitelisted IP addresses can be
         spidered.
@@ -526,7 +531,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             channel.json_body, {"og:title": "~matrix~", "og:description": "hi"}
         )
 
-    def test_blacklisted_ip_with_external_ip(self):
+    def test_blacklisted_ip_with_external_ip(self) -> None:
         """
         If a hostname resolves a blacklisted IP, even if there's a
         non-blacklisted one, it will be rejected.
@@ -549,7 +554,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_blacklisted_ipv6_specific(self):
+    def test_blacklisted_ipv6_specific(self) -> None:
         """
         Blacklisted IP addresses, found via DNS, are not spidered.
         """
@@ -572,7 +577,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_blacklisted_ipv6_range(self):
+    def test_blacklisted_ipv6_range(self) -> None:
         """
         Blacklisted IP ranges, IPs found over DNS, are not spidered.
         """
@@ -591,7 +596,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_OPTIONS(self):
+    def test_OPTIONS(self) -> None:
         """
         OPTIONS returns the OPTIONS.
         """
@@ -601,7 +606,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         self.assertEqual(channel.code, 200)
         self.assertEqual(channel.json_body, {})
 
-    def test_accept_language_config_option(self):
+    def test_accept_language_config_option(self) -> None:
         """
         Accept-Language header is sent to the remote server
         """
@@ -652,7 +657,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             server.data,
         )
 
-    def test_data_url(self):
+    def test_data_url(self) -> None:
         """
         Requesting to preview a data URL is not supported.
         """
@@ -675,7 +680,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
 
         self.assertEqual(channel.code, 500)
 
-    def test_inline_data_url(self):
+    def test_inline_data_url(self) -> None:
         """
         An inline image (as a data URL) should be parsed properly.
         """
@@ -712,7 +717,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         self.assertEqual(channel.code, 200)
         self._assert_small_png(channel.json_body)
 
-    def test_oembed_photo(self):
+    def test_oembed_photo(self) -> None:
         """Test an oEmbed endpoint which returns a 'photo' type which redirects the preview to a new URL."""
         self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
         self.lookups["cdn.twitter.com"] = [(IPv4Address, "10.1.2.3")]
@@ -771,7 +776,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         self.assertEqual(body["og:url"], "http://twitter.com/matrixdotorg/status/12345")
         self._assert_small_png(body)
 
-    def test_oembed_rich(self):
+    def test_oembed_rich(self) -> None:
         """Test an oEmbed endpoint which returns HTML content via the 'rich' type."""
         self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
 
@@ -817,7 +822,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_oembed_format(self):
+    def test_oembed_format(self) -> None:
         """Test an oEmbed endpoint which requires the format in the URL."""
         self.lookups["www.hulu.com"] = [(IPv4Address, "10.1.2.3")]
 
@@ -866,7 +871,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             },
         )
 
-    def test_oembed_autodiscovery(self):
+    def test_oembed_autodiscovery(self) -> None:
         """
         Autodiscovery works by finding the link in the HTML response and then requesting an oEmbed URL.
         1. Request a preview of a URL which is not known to the oEmbed code.
@@ -962,7 +967,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         )
         self._assert_small_png(body)
 
-    def _download_image(self):
+    def _download_image(self) -> Tuple[str, str]:
         """Downloads an image into the URL cache.
         Returns:
             A (host, media_id) tuple representing the MXC URI of the image.
@@ -995,7 +1000,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         self.assertIsNone(_port)
         return host, media_id
 
-    def test_storage_providers_exclude_files(self):
+    def test_storage_providers_exclude_files(self) -> None:
         """Test that files are not stored in or fetched from storage providers."""
         host, media_id = self._download_image()
 
@@ -1037,7 +1042,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             "URL cache file was unexpectedly retrieved from a storage provider",
         )
 
-    def test_storage_providers_exclude_thumbnails(self):
+    def test_storage_providers_exclude_thumbnails(self) -> None:
         """Test that thumbnails are not stored in or fetched from storage providers."""
         host, media_id = self._download_image()
 
@@ -1090,7 +1095,7 @@ class URLPreviewTests(unittest.HomeserverTestCase):
             "URL cache thumbnail was unexpectedly retrieved from a storage provider",
         )
 
-    def test_cache_expiry(self):
+    def test_cache_expiry(self) -> None:
         """Test that URL cache files and thumbnails are cleaned up properly on expiry."""
         self.preview_url.clock = MockClock()